Ili parolis pri la batalo.

In Esperanto, -is marks the past tense.

So:

• paroli = to speak / to talk
• parolas = speaks / is speaking / talks
• parolis = spoke / was speaking / talked

So Ili parolis means they spoke or they were talking.

Because Esperanto verbs do not change according to the subject.

That means:

• mi parolis = I spoke
• vi parolis = you spoke
• li parolis = he spoke
• ili parolis = they spoke

The verb stays parolis no matter who is doing the action.
Ili is simply the pronoun meaning they.

The verb paroli is commonly used with the preposition pri, meaning about.

So:

• paroli pri io = to talk about something

That is why Esperanto uses:

• Ili parolis pri la batalo = They talked about the battle

Not:

• Ili parolis la batalon

That would sound wrong for the meaning talked about the battle.

Pri means about, concerning, or regarding.

In this sentence, it introduces the topic of the talking:

• parolis pri la batalo = talked about the battle

It is a very common preposition in Esperanto.

La is the definite article, meaning the.

So:

• batalo = a battle / battle
• la batalo = the battle

If the intended meaning is a specific battle already known from context, Esperanto uses la, just like English uses the.

There is no -n because la batalo is not the direct object of the verb. It comes after the preposition pri.

Normally, nouns after a preposition do not take -n:

• pri la batalo
• kun amiko
• en la domo

So batalo stays batalo, not batalon.

Batalo is built from:

• batal- = battle / fighting
• -o = noun ending

So batalo is a noun meaning battle.

This is a very common pattern in Esperanto:

• parol-o = speech
• amik-o = friend
• dom-o = house

Yes, Esperanto word order is fairly flexible, although the most neutral order is:

• Ili parolis pri la batalo.

You could also see something like:

• Pri la batalo ili parolis.

That would put more emphasis on the battle as the topic.

Still, for learners, the standard subject + verb + prepositional phrase order is the safest and most natural choice.

A simple pronunciation guide is:

EE-lee pah-ROH-lees pree lah bah-TAH-lo

A few helpful points:

• i sounds like ee
• a sounds like ah
• o sounds like oh
• stress usually falls on the second-to-last syllable

So:

• Ili → EE-lee
• parolis → pah-ROH-lees
• batalo → bah-TAH-lo

Yes. Esperanto tense endings mainly show time, not the English-style distinction between simple and continuous forms.

So parolis can correspond to:

• spoke
• talked
• was talking
• were talking

The exact nuance usually comes from context.